Inmate Robert Knowles pitches plant stalks into a compost pile Oct. 17 at the Cedar Creek Corrections Center in rural southwest Washington. The minimum-security prison has adopted many environmental and cost-saving practices.

Littlerock, Wash. ? Of all the things convicted murderer Robert Knowles has been called during his 13 years behind bars, recycler hasn’t been one of them.

But there he was one morning, pitchfork in hand, composting food scraps from the main chow line and coffee grounds from prison headquarters – doing his part to “green” the prison.

“It’s nice to be out in the elements,” said Knowles, 42, stirring dark, rich compost that will amend the soil at the small farm where he and fellow inmates of the Cedar Creek Corrections Center grew 8,000 pounds of organic vegetables this year.

Inmates of the minimum-security facility, 25 miles from Olympia, the state capital, raise bees, grow organic tomatoes and lettuce, compost 100 percent of food waste and even recycle shoe scraps that are made into playground turf.

“It reduces cost, reduces our damaging impact on the environment, engages inmates as students,” said Eldon Vail, secretary of the Washington Department of Corrections, which oversees 15 prisons and 18,000 offenders. “It’s good security.”

As around-the-clock operations, prisons are voracious resource hogs, and administrators are under increasing pressure to reduce waste and conserve energy and water.

In 2007, states spent more than $49 billion to feed, house, clothe, treat and supervise 2.3 million offenders, the Pew Center on the States reported this year.

As the prison population has grown this decade, up 76 percent from 1.3 million in 2000, the number of prisons and jails has risen with it. The latest U.S. Bureau of Justice data show 1,821 facilities in 2005, up from 1,668 in 2000.

To keep costs down, the Indiana Department of Corrections installed water boilers that run on waste wood chips and built a wind turbine at one prison that generates about 10 kilowatts an hour and saves $2,280 a year.

At Ironwood State Prison in Blythe, Calif., 6,200 solar panels send energy back to the grid, enough to power 4,100 homes a year. The prison was trying to meet an executive order requiring state agencies to reduce energy use by 20 percent by 2015, said a spokeswoman, Lt. Sue Smith.

Under a state mandate to reduce energy use, the Oregon Department of Corrections replaced old appliances with energy-efficient ones, installed solar water heaters and used a geothermal well to heat water. It also modified washing machines so they could reuse rinse-water to wash about a million pounds of clothes a month.

At Eastern Oregon Correctional Institution in Pendleton, Ore., inmates recycle scraps from old prison blues to make diaper bags for women’s shelters and dog beds for animal shelters.

“We try to model prosocial behavior,” said Vern Rowan, business manager for the Oregon Department of Corrections. Being sustainable “is something that everybody should be doing, regardless of where they’re at.”

Cedar Creek, in the heart of a forest, feels more like an outdoor retreat than institutional lockup.

Most of the 400 inmates are in a work program and put in between six and eight hours a day.

The responsibility of caring for the prison’s three hives of Italian honey bees falls mostly to Daniel Travatte, 36, a soft-spoken former drug addict who is serving 10 years for attempted armed robbery.

“I’m trying to change myself,” Travatte said. “A lot of people go through prison with no intention of changing. I love working with the bees.”